For the past 20 years, a CCD image sensor has monopolized an image sensor market, but it is predicted that a CMOS image sensor market remarkably grows to exceed a CCD image sensor in an amount and the sales in a mobile field requiring for a low electric power consumption. Especially, a rapidly increasing number of CMOS image sensors are used in the specified fields requiring for a high function and a high integration, a high speed/high pixel characteristic and so on. The major markets of this field include a mobile phone, a digital steel camera, an optical mouse, a surveillance camera, biometrics and so on.
A CMOS image sensor is manufactured into a CMOS image sensor module from a CMOS image sensor chip by an electronic package technology. And it is applied into various goods and a package specification required by the CMOS image sensor module depends on characteristics of the finished goods. Especially, the recent tendencies of a CMOS image sensor module, namely, high electricity capabilities, miniaturization/high density, a low power consumption, multifunction, a high speed signal processing, a reliability are the representative characteristics of a miniaturization of the electronic goods.
Contrary to general CMOS chips, the CMOS image sensor in the past is feasible to a physical environment and can be polluted by the impurities, and a leadless chip carrier LCC type package is used when its size is not considered to be important. However, in a recent tendency of a market requiring for thin and simplified characteristics such as in a camera phone, chip-on-board (COB), chip-on-film (COF), chip size package (CSP), etc. are generally used.
FIG. 1 is a perspective view showing the structure of an image sensor module using a COB method and a COF method of an image sensor.
In the COB method, a flexible PCB 103 is adhered to a rear surface of an image sensor chip 101 by a die paste, and input/output (I/O) terminals of an image sensor chip 101 is connected with the PCB electrode by a gold bonding wire 102. The method is advantageous in that a productivity is improved in a process similar to the existing semiconductor production line but disadvantageous in that the size of a module is increased because a space for wire bonding is required. In the COB method, a flexible PCB is directly adhered to an image sensor chip 101, but in the COF method, an active side of an image sensor chip 101 is directly flip-chip bonded to an electrode of a flexible PCB or a flexible printed circuit (FPC). Therefore, a gold bonding wire 102 is not required contrary to the COB method and the height of a body tube is lowered to manufacture a thin and short module. At this time, an anisotropic conductive film (ACF) is primarily used to attach an image sensor to a flexible PCB or FPC, and a gold plating bump or an electroless nickel/gold bump are used for a bump formed on input/output (I/O) terminals of the image sensor chip 101. In addition, the flexible PCB or FPC has a perforated portion as wide as a sensing portion in order to transmit a light into a front portion of an image sensor.
FIG. 2 is a perspective view showing a CSP package structure for an image sensor module developed by Shellcase Inc. of Israel.
In order to realize a thin and short chip package of an image sensor, a chip size package technology is developed. As shown in FIG. 2, the CSP method of which the original patent is owned by Shellcase Inc. of Israel has an image sensor chip 201 mounted on a lower glass substrate 205, an empty space between an image sensing portion and an upper glass substrate 202, of which peripheral portions are adhered by epoxy resin to form an electric wiring at a rear surface of a substrate glass from input/output (I/O) and a solder bump 204 is finally formed. A wafer level process can be performed in order to simplify the manufacture of a module and the CSP method is helpful to decrease a volume of the module. However, an upper glass substrate 202 and a lower glass substrate 205 are used respectively not enough to further decrease the height of an image sensor module.
FIG. 3 is a perspective view showing the structure of an image sensor module using a COG method in an image sensor.
Recently, a glass for an IR filter is combined with a substrate to develop a package in a Chip-on-Glass (COG) method in an attempt to decrease the size of a module of an image sensor as shown in FIG. 3. In other words, an electrode and a wiring are formed on a glass substrate 303 having the shape of a wafer, a solder bump 301 for the second connection is adhered to the glass substrate 303 and an image sensor chip 302 where a solder bump is formed at the input/output (I/O) terminals is flip-chip bonded to the glass substrate 303 and the glass substrate 303 having the image sensor chip 302 is diced to manufacture an image sensor module. The image sensor module manufactured in this method is advantageous in that the thickness can be minimized but is disadvantageous in that the width is increased because a wider glass module substrate than an image sensor chip is used. In a strict meaning, it cannot be called a wafer level package because a separate chip contacts a glass wafer substrate.